The aim of this research proposal is to assess some of the morphological and neurophysiological correlates of the aging process in the central nervous system. To study these the basal ganglia will be used as a model system. In one set of experiments we will determine the effects of the aging process on the cytoarchitectural and ultrastructural characteristics of basal ganglia neurons in cats. In a second set of experiments the effects of the aging process on the neurophysiological characteristics of basal ganglia neurons in cats will be determined. Wherever possible the morphological and functional alterations that occur in aged animals will be correlated to provide a picture of the neuronal dysfunctions that occur in senescence. In a third set of experiments th anatomical and physiological effects of aging will be related to some of the neurological disturbances that occur.